焊缝梯度过渡激光焊接Ti3Al基合金与GH4169异种材料的界面冶金及机理

Considering the quite different chemical compositions, thermo-physical properties and mechanical properties of Ti3Al-based alloy and Ni-based superalloy, joining these two materials is a great challenge. Therefore it is of great importance to take measures to solve the problems about the interface metallurgical compatibility and effectively control the interface metallurgical behaviors, to realize reasonable transitions of the joint interfaces and to achieve a sound joining between the two dissimilar materials. . In this project, a method of decreasing the formation tendency of brittle intermetallics across the joint interface of Ti3Al-based alloy and Ni-based superalloy is newly proposed. That is, firstly, alloys with different chemical compositions are laser cladded on the surface of the joined Ti3Al base alloy layer by layer and a graded structure is thus formed, in which the chemical composition owns a gradual transition from that of Ti3Al to the one close to the joined Ni-based superalloy. Subsequently, the surface layer of the graded structure and the Ni-based superalloy are laser welded using a suitable filler alloy. It is believed that our method can avoid the formation of brittle intermetallics at the joint interface and obtain a sound joint of Ti3Al-based alloy and Ni-based superalloy.. This project will provide technical reserves for realizing the applications of dissimilar joint structures between Ti3Al-based alloy and Ni-based superalloy in the productions of aeroengines. The microstructure evolution and elements distribution profiles along the laser welded joint with a graded weld bead will be studied, the relationship between the chemical compositions of the alloys and their metallurgical compatibilities will be analyzed and the effects and corresponding mechanisms on the interface combination quality and mechanical properties of the joints will be revealed. Therefore, this project is theoretically valuable and has great importance for engineering applications.

对于化学成分和物理、力学性能差异很大的Ti3Al基合金与Ni基高温合金组合连接，如何解决异种材料界面的冶金相容性问题并进行有效的界面冶金控制，以实现界面的合理过渡并获得良好接头，是值得研究的科学问题。. 本项目提出利用激光熔覆技术在被焊Ti3Al基合金表面逐层熔覆具有不同成分的合金层，制备出梯度过渡结构，成分逐渐向接近被焊Ni基高温合金成分的方向过渡，然后对梯度过渡结构与Ni基高温合金进行激光添丝焊接，从根本上避免在焊接界面产生脆性金属间化合物，最终实现两种母材的完好连接。. 本项目将为实现Ti3Al基合金代替Ni基高温合金在航空航天发动机上的应用提供技术储备，通过深入研究梯度过渡焊缝的微观组织演变及元素分布规律，分析合金成分及冶金相容性之间的内在联系，揭示梯度过渡结构对改善Ti3Al/Ni基高温合金接头界面结合质量及力学性能的作用机理，具有重要的现实工程意义和科学研究价值。

本项目针对具有较大难度的Ti3Al基合金与镍基高温合金异种材料之间的焊接，采用多种合金作为焊料对Ti3Al/GH4169添丝氩弧焊技术进行了研究，得到了Ni、Cu、Ti、Nb、Ag、Cr、Al、Fe、W等多种元素对焊接过程界面冶金行为的影响规律。.在此基础上，提出了焊缝梯度过渡Ti3Al/GH4169焊接的创新性实验思路。通过在Ti3Al基合金表面逐层堆焊成分逐渐变化的中间层合金的方法，在被焊Ti3Al母材表面制备了梯度过渡结构，然后对梯度过渡结构的表层与GH4169母材进行添丝氩弧焊，成功获得了具有梯度过渡结构焊缝的Ti3Al/GH4169接头。各合金层之间、合金层与母材之间均形成了良好的冶金结合，有效避免了在直接焊接的界面产生脆性的金属间化合物，不仅成功实现了两种母材之间的完好焊接，同时接头的强度也有了较大程度的提高。接头的平均室温抗拉强度为353MPa，600℃下的平均强度值为245MPa。.在氩弧焊实验研究的基础上，采用金属粉末作为焊料，开展了Ti3Al/GH4169异种材料激光焊接技术研究。对接头的微观组织及元素分布进行了观察和分析，测试了接头的维氏显微硬度和室温抗拉强度，对断裂位置及断裂特征进行了研究。根据项目研究结果，对梯度过渡结构提出了优化思路。.本项目通过重点研究和改善Ti3Al基合金与镍基高温合金GH4169异种材料焊接过程的界面冶金行为，显著改善了接头的微观组织和力学性能，为直接解决几乎不可焊的Ti3Al/镍基高温合金组合奠定了坚实的基础，为实现Ti3Al基合金代替镍基高温合金的异种材料焊接结构在航空、航天发动机上的应用提供了技术储备，也为设计所在发动机相关耐热部件的设计和应用方面提供了更大的灵活性和可行的技术途径。 .此外，本项目通过对Ti3Al/GH4169接头微观组织演变及梯度过渡结构界面冶金行为的分析研究，获得了合金成分与冶金相容性之间的内在联系，揭示了梯度过渡焊缝的组织结构及元素分布对改善接头界面结合质量及力学性能的作用机理，对于更广阔范围内的异种材料组合连接具有借鉴意义。

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